Many investigators at Johns Hopkins (JHU) have urgent need for routine access to high sensitivity mass spectrometric analytical capabilities. The Basic Science departmental leadership, with the strong support of the Admin., are establishing a true open-access, state-of-the-art, mass spectrometric facility. In phase I of this plan, several major users, the Dean's office, and Biological Chemistry have collectively purchased a Perseptive MALDI-TOF DE instrument. As part of phase II, funds are requested to purchase a Micromass Q-TOF electrospray time of flight mass spectrometer. The complimentary capabilities of these two types of MS will greatly enhance progress of many varied NIH supported research programs at JHU. The unique capabilities of the Q-TOF MS are essential to many of these investigations. The MS Facility and the Q-TOF will be directed by an Instructor level faculty member with extensive MS expertise. The MALDI-TOF will continue to be operated/supervised by an experienced full-time technician. The P.I. and co-P.I. will meet at-least weekly with the facility staff to discuss technical issues, workload, and priorities. An oversight committee comprised of the P.I., co-P.I., the Director of the JHU protein facility, and three Dept. Directors, who are also major users, will meet monthly to discuss policy and problems. Outside expert review will be sought at the end of the first year. Staff support will be maintained at at- least this level. Instrumentation will be kept on full service agreements for their useful lifespans. Use charges of $50/h for MALDI-TOF and $100/sample for Q-TOF MS-MS (includes data analysis) will be returned to the facility. The MS facility will service over 110 NIH-funded laboratories. Ten major and ten typical minor users are identified. Priority will be determined by chronology, but with major users given precedence. A week-long MS course will be presented to faculty, students, and postdoc. fellows concomitant with the facility opening.